Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C243/00—Compounds containing chains of nitrogen atoms singly-bound to each other, e.g. hydrazines, triazanes
  • C07C243/04—N-nitroso compounds
  • C07C243/06—N-nitroso-amines
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/50—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/62—Use of additives, e.g. for stabilisation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S203/00—Distillation: processes, separatory
  • Y10S203/03—Acrylonitrile
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S203/00—Distillation: processes, separatory
  • Y10S203/10—Vinyl acetate
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S203/00—Distillation: processes, separatory
  • Y10S203/22—Accessories

Definitions

• This invention relates to compounds and compositions useful as polymerization inhibitors for acrylic acids and esters thereof. It also is concerned with a method for inhibiting polymerization of acrylic acids and esters thereof, particularly on a manufacturing scale, by use of these compounds and compositions.
• Acrylic acid, methacrylic acid, and esters thereof have wide application as raw materials for fibers and plastics. Since these compounds have reactive unsaturated bonds in their molecules they are prone to polymerize under the conditions encountered during purification, manufacturing or storage.
• Commercial processes for the manufacture of acrylic and methacrylic acids and esters typically produce products contaminated with various impuruties. These impurities must be removed in order for the monomer product to be suitable for most applications. Such purification is generally accomplished by distillation.
• Polymerization is likely to occur during distillation and may occur as a result of the presence of heat, light, oxygen and other conditions. It is therefore most desirable to minimize or eliminate the tendency of acrylic acids or acrylates to polymerize during manufacturing, thus assuring that the vessels and pipes used to transport the material during production remain clean and the reactors free of build up of high viscosity, high molecular weight, polymerized material.
• Japanese patent application 48-35699 is directed to the stabilization of styrene, chloroprene, butadiene, isoprene, or acrylic acid derivatives with various compounds including certain N,N'-dinitroso compounds.
• Japanese patent application 48-38399 is directed to stabilization of acrylates or methacrylates with certain N-nitrosoamine compounds.
• U.S. Patent 3,816,267 is directed to inhibition of acrylate polymerization during distillation by the use of a quinone and an enol derivative of a quinone.
• U.S. Patent 4,338,162 is directed to the inhibtion of vinyl polymerization of a 2-isocyanatoalkyl ester of unsaturated carboxylic acid with certain nitrogen oxides.
• U.S. Patent 3,959,358 is directed to polymerization inhibition of acrylate esters by use of an alkyl-substituted phenolic compound.
• This invention is directed to N,N'-dinitroso phenylenediamine compounds useful as polymerization inhibitors, which have the following structure (I): wherein R is C1-C12 alkyl or C6-C10 aryl; R1 is C1-C12 alkyl, C6-C10 aryl, C7-C11 aralkyl, and C7-C16 alkaryl.
• This invention is also directed to polymerization inhibitor compositions comprising:
• this invention is directed to an acrylic or methacrylic acid or ester composition stabilized against polymerization by an effective amount of a compound having structure I or by an effective amount of composition I.
• this invention is directed to a method for inhibiting polymerization of an acrylic or methacrylic acid or ester composition, said method comprising adding an effective amount of the polymerization inhibitor of structure I or composition I.
• N,N'-dinitroso phenylenediamine derivatives may be prepared from phenylenediamine, sodium nitrite, and a suitable mineral acid (such as sulfuric or hydrochloric), as more fully set forth below in Examples 1-3.
• Preferred N,N'-dinitroso phenylenediamine compounds include those wherein the amine groups are in the para position. Particularly preferred are compounds wherein R is C3-C7 alkyl and R1 is phenyl or C3-C7 alkyl.
• N,N'-dinitroso phenylenediamine compounds which may be employed include N-phenyl-N'-isopropyl dinitroso-p-phenylenediame, N-phenyl-N'-(1,3-dimethylbutyl) dinitroso-p-phenylenediamine, N-phenyl-N'-(1,4-dimethylpentyl)-dinitroso-p-phenylenediamine, and N,N'-bis (1,4-dimethylpentyl)-dinitroso-p-phenylenedimine. Moreover, mixtures of N,N'-dinitroso phenylenediamines may be employed.
• phenothiazine compounds are generally known, and their synthesis would be readily apparent to one skilled in the art.
• Particularly suitable phenothiazine compounds which may be employed in the compositions of the present invention include phenothiazine, 2-methylphenothiazine, 2-octylphenothiazine, 2-nonylphenothiazine, 2,8-dimethylphenothiazine, 3,7-dimethylphenothi azine, 3,7-diethylphenothiazine, 3,7-dibutylphenothiazine, 3,7-dioctylphenothiazine, 2,8-dioctylphenothiazine, 3,7-dinonylphenothiazine, 2,8-dinonylphenothiazine, 2(alpha,alpha-dimethylbenzyl) phenothiazine, 3,7-bis-(alpha,alpha-dimethylbenzyl
• hydroquinone or hydroquinone monomethyl ether are compounds which are known as antioxidants and, specifically, as monomer stabilizers. They have been used as shelf stabilizers for acrylic monomers.
• phenylenediamine compounds are also generally known, and their synthesis would be readily apparent to one skilled in the art.
• Preferred phenylenediamine compounds include those wherein the amine groups are in the para position.
• Particularly preferred compounds are the para-phenylenediamines wherein R7 and R8 are hydrogen; R6 is alkyl or phenyl; and R9 is C3-C8 alkyl or C3-C8 cycloalkyl.
• phenylenediamine compounds which may be employed include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamlne, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N'-(1,4-dimethylpentyl)-p-phenylenediamine and N-phenyl-N'-cyclohexyl-p-phenylenediamine. Moreover, mixtures of phenylenediamine compounds may also be employed.
• the phenylenediamine compounds may be of the oxygenated species as described in U.S. Pat. 4,774,374 to Abruscato et al.
• the N,N'-dinitroso phenylenediamine and phenothiazine/hydroquinone compounds are generally employed in weight ratios of between 10:1 and 1:10. Preferably, weight ratios of between 4:1 and 1:4 are employed. Most preferred ratios include those from 3:1 and 1:3. If a phenylenediamine is employed, it is generally present in weight ratios of between 10:1 and 1:10, based on the weight of N,N'-dinitroso phenylenediamine.
• the polymerization inhibitor compositions of this invention may further comprise a solvent such as toluene, MIBK (methyl isobutyl ketone), isobutyl acetate, isopropyl ether, acrylic acid, methacrylic acid, water, and the like.
• a solvent such as toluene, MIBK (methyl isobutyl ketone), isobutyl acetate, isopropyl ether, acrylic acid, methacrylic acid, water, and the like.
• a primary use of the polymerization inhibitor compounds and compositions of this invention is to prevent the polymerization of acrylic and methacrylic acid and esters thereof during their purification by distillation to remove unreacted starting materials and distillable by-products.
• this involves the sequential distillation of the acrylic or methacrylic acid or ester reaction product through a plurality of distillation columns. In the first of such columns, a relatively large amount of starting material and by-products will be present, while in the last column essentially pure acrylic acid or ester compound, plus polymerization inhibitors and heavy, nondistillable by-products, will be present.
• the method of this invention involves adding to an acrylic or methacrylic acid or ester an effective amount of the polymerization inhibitor compound or composition described herein.
• an effective amount of the polymerization inhibitor compound or composition described herein When the polymerization inhibitor composition of this invention is employed with a hydroquinone compound and/or a phenylenediamine during the purification or distillation of the acrylic acid or ester, it is preferred that oxygen, whether in the form of air (either added or ambient) or otherwise, be present. It is noted that the polymerization inhibitor compounds and compositions of this invention will be effective for uses other than distillation, for example during shipment or storage of the acrylic compound.
• the method of this invention entails the addition of an effective amount of a polymerization inhibitor compound or composition to acrylic or methacrylic acid or esters thereof.
• a polymerization inhibitor compound or composition to acrylic or methacrylic acid or esters thereof.
• amount of polymerization inhibitor required will vary somewhat, based on such factors as the particular N,N'-dinitroso phenylenediamine and the phenothiazine/hydroquinone species employed, such an effective amount may be readily determined by experimentation. Generally, such an effective amount will be between about 50 and 5,000 parts per million by weight of acrylic/methacrylic compound.
• the polymerization inhibitor compounds and compositions of this invention will provide stability against polymerization at temperatures typically employed for purification of acrylic acids amd esters, from about 90° to about 140°C, for time periods in excess of those typically employed for such purifications.
• Example 2 The procedure detailed in Example 1 was followed, except a 60/40 blend of N-phenyl-N'-(1,4-dimethylpentyl) p-phenylenediamine and N-phenyl-N'-(1,3-dimethylbutyl) p-phenylenediamine was used. The stirring time was lengthened to two hours. The solid was collected by filtration and washed well with water. Recrystallization from methanol yielded a solid with a melting point of 51-56°C.
• the following test is an initial screening procedure which is a timed test to determine how long it takes for polymerization to occur, which is a measure of inhibitor efficiency.
• shelf inhibitor is removed from acrylic acid by distillation. A 0.1% stock solution of each inhibitor in acrylic acid is prepared. Solutions containing 10 ppm inhibitor are prepared from the stock solutions and put in a test tube.
• the compounds and compositions of this invention are shown to be polymerization inhibitors in various distillation procedures.
• the distillation screening apparatus used in these examples consists of a distillation pot fitted with a tray distillation column, pot thermometer, graduated addition funnel, inhibitor addition funnel, magnetic stirrer, and a bottom vacuum take-off.
• the distillation column was fitted with a distillation head consisting of a thermometer, cold finger, vacuum take-off, inhibitor addition funnel, and valved condensate vacuum take-off.
• the contents of the pot is distilled at 105°C under reduced pressure.
• the distillation is run at a 1:4 reflux rate.
• Acrylic acid is removed from the overhead at a rate of 1 ml/min and the addition of acrylic acid to the distillation pot is also 1 ml/min to maintain a constant pot volume.
• Acrylic acid containing 20,000 ppm of phenothiazine and 20,000 ppm of hydroquinone is added to the system at a rate of 10 ml/hr directly to the cold finger in the overhead to protect the column from polymerization.
• the tested inhibitor is added directly to the acrylic acid in the distillation pot at a rate of 10 ml/hr. Air is added to the distillation pot at a rate of approximately 8 ml/min. The distillation is run for 5 hours. The columns, pot, dead space, and overhead were inspected hourly for the formation of any polymer.
• the contents of the pot is distilled at 105°C under 185 mm Hg.
• the distillation is run at a 1:4 reflux rate.
• Acrylic acid is removed from the overhead at a rate of 12 ml/hr and removed from the bottoms at a rate of 48 ml/hr.
• Acrylic acid is added to the distillation pot at a rate of 60 ml/hr to maintain a constant pot volume.
• Freshly distilled acrylic acid containing 500 ppm of phenothiazine is added to the system at a rate of 10 ml/hr directly to the cold finger in the overhead to protect the column from polymerization.
• the inhibitor is added directly to the acrylic acid in the distillation pot at a rate of 10 ml/hr.
• acrylic acid 500 grams are placed in the distillation pot. Approximately 0.04 grams of seed polymer (polyacrylic acid) is placed in a stainless steel basket with a lid and suspended in the overhead section to eliminate contact with liquid material. Sixty ml/hr of freshly distilled acrylic acid is added. The take/off rate is 60 ml/hr from the overhead, which is approximately a 1:4 ratio.
• the distillation is carried out at 105°C and 185 mm Hg for a test period of five hours.
• Phenothiazine and hydroquinone (2% each by weight in acrylic acid is added at the midpoint of the condenser for protection of the column from polymerization) at a rate of 10 ml/hr. 400 ppm of each of these substances are also added to the bottoms to eliminate polymer formation in the pot.
• the seed is washed well with methanol, dried to constant weight in a vacuum oven, and reweighed. Percent seed growth is calculated to determine if the polymer seed is active.
• compositions of the present invention exhibit unexpected activity.
• the combination of phenothiazine and hydroquinone gave good results and was chosen as a candidate for the distillation tests of Examples 5-7, where it gave unacceptable performance.
• Compounds 1 and 2 gave unacceptable results in the Example 4 polymerization onset test, and thus would not normally be considered as viable inhibitor candidates in the distillation tests.
• phenothiazine and hydroquinone which is closer to the actual use situations where polymerization inhibition in production and purification of acrylic compounds is needed, acceptable results are surprisingly obtained.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Polymerisation Methods In General (AREA)

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Publications (3)

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Cited By (9)

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Citations (6)

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• 1992
  • 1992-06-05 EP EP92305201A patent/EP0522709B1/de not_active Expired - Lifetime
  • 1992-06-05 DE DE69212925T patent/DE69212925T2/de not_active Expired - Lifetime
  • 1992-06-05 CA CA002070551A patent/CA2070551C/en not_active Expired - Lifetime
  • 1992-06-05 AT AT92305201T patent/ATE141588T1/de active
  • 1992-07-10 JP JP4184087A patent/JPH0751604B2/ja not_active Expired - Fee Related
• 1993
  • 1993-09-02 US US08/115,388 patent/US6210536B1/en not_active Expired - Fee Related

Patent Citations (6)

Non-Patent Citations (5)

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